Identification of integrated circuits using pixel or memory cell characteristics

ABSTRACT

Disclosed are various embodiments of methods and corresponding devices for effecting such methods that permit integrated circuits, sensors, chips or dies to be identified. Imperfections or irregularities in pixels or memory cells are used to generate identification codes for integrated circuits, sensors, chips or dies. Addresses or data locations of selected defective pixels or memory cells may be used to generate such identification codes.

FIELD OF THE INVENTION

The present invention relates to the field of identifying semiconductorsensors, integrated circuits, dies and chips.

BACKGROUND

Semiconductor dies often need to be identified for a variety of reasons,including, but not limited to, tracking dies during manufacturing,tracking die inventories, determining the date upon which a particulardie or group of dies was manufactured, determining the particularmanufacturing batch corresponding to a particular die, and so on.Identification information ideally permits a particular semiconductordie, either during or after manufacturing, to be identified with 100%confidence. Once a particular die has been identified, other informationpertaining to the die may be retrieved or used, such as the die's dateof manufacture, manufacturing batch information associated with the die,the date the die was shipped from the foundry, royalty informationassociated with the die, and other information.

Most current semiconductor die identification methods use non-volatilestorage elements, such as RFID tags, fuses or non-volatile memories tostore die identification information or tags. These methods generallyrequire that additional circuitry for storing such information beincorporated into the die. They also generally involve extra tasks suchas programming non-volatile elements. As a result, prior art dieidentification methods can involve considerable costs due to the need toprovide extra circuitry and extra test and programming time.

One example of a prior art method of identifying semiconductor dies isprovided by SiidTech Inc. of Hilsboro, Oreg., who employ “siliconfingerprinting technology” to trace semiconductor dies, and incorporatesuch technology into RFID circuits, smart cards and badges and hardwarekeys. Still other applications include tagging, authentication andintellectual property tagging.

Various patents containing subject matter relating directly orindirectly to the field of the present invention include, but are notlimited to, the following:

U.S. Pat. No. 6,161,213 for System for providing an integrated circuitwith a unique identification to Lofstrom.

U.S. Pat. No. 5,051,895 for Apparatus and method for tracking andidentifying printed circuit assemblies to Rogers.

U.S. Pat. No. 5,079,725 for Chip identification method for use with scandesign systems and scan testing techniques to Geer at al.

U.S. Pat. No. 5,301,143 for Method for identifying a semiconductor dieusing an IC with programmable links to Ohri et al.

U.S. Pat. No. 5,350,715 for Chip identification scheme to Lee.

U.S. Pat. No. 5,553,022 for Integrated circuit identification apparatusand method to Weng et al.

U.S. Pat. No. 5,642,307 for Die identifier and die identification methodto Jernigan.

U.S. Pat. No. 5,742,526 for Apparatus and method for identifying anintegrated device to Voshell et al.

U.S. Pat. No. 5,818,738 for Method for testing the authenticity of adata carrier having an integrated circuit to Effing et al.

U.S. Pat. No. 5,895,962 for Structure and a method for storinginformation in a semiconductor device to Zheng et al.

U.S. Pat. No. 6,147,316 for Method for sorting integrated circuitdevices to Beffa.

U.S. Pat. No. 6,190,972 for Method for storing information in asemiconductor device to Zheng et al.

U.S. Pat. No. 6,365,421 for Method and apparatus for storage of testresults within an integrated circuit to Debenham et al.

U.S. Pat. No. 6,601,008 for Parametric device signature to Madge.

U.S. Pat. No. 6,710,284 for Laser marking techniques for baresemiconductor die to Farnworth et al.

U.S. Pat. No. 6,812,477 for Integrated circuit identification toMatsunami.

U.S. Pat. No. 6,813,058 for Method and apparatus for personalization ofsemiconductor to Sandstrom.

U.S. Pat. No. 6,830,941 for Method and apparatus for identifyingindividual die during failure analysis to Lee at al.

U.S. Pat. No. 6,889,305 for Device identification using a memory profileto Andelmann.

U.S. Pat. No. 6,941,536 for Method for identifying semiconductorintegrated circuit device, method for manufacturing semiconductorintegrated circuit device, semiconductor integrated circuit device andsemiconductor chip to Muranaka.

U.S. Pat. No. 6,960,753 for Photosensor arrays with encoded permanentinformation to Cheung.

U.S. Pat. No. 6,990,387 for Test system for identification and sortingof integrated circuit devices to Freij et al.

U.S. Pat. No. 6,944,567 for Method in an integrated circuit (IC)manufacturing process for identifying and redirecting ICs mis-processedduring their manufacture to Beffa.

U.S. Pat. No. 6,996,484 for Sequential unique marking to Raitter.

U.S. Pat. No. 7,015,795 for Self-identifying integrated circuits andmethod for fabrication thereof to Doudoumopolous.

U.S. Pat. No. 7,017,043 for Methods and systems for the identificationof circuits and circuit designs to Potkonjak.

What is needed is a method and device for tracking semiconductor diesduring and after manufacturing that is accurate and inexpensive, andthat does not require additional circuitry on, or additional programmingof, the dies. Upon having read and understood the Summary, DetailedDescriptions and Claims set forth below, those skilled in the art willappreciate that at least some of the devices and methods disclosed inthe printed publications listed herein may be modified advantageously inaccordance with the teachings of the present invention.

SUMMARY

In a first embodiment of the present invention, there is provided afirst method of generating an identification tag corresponding to aselected imaging sensor. The sensor comprises a first array of imagepixels and a second array of reference pixels, where the first array isconfigured to capture images and the second array is configured topermit black or dark level compensation of images captured by the firstarray. Each reference pixel has a dark current value and an addressassociated therewith. The first method comprises providing the selectedimaging sensor; downloading dark signal values and addressescorresponding thereto from the second array; selecting, from among thedark signal values and addresses corresponding thereto, selected darksignal values and addresses corresponding thereto; and generating, fromthe selected dark signal data and addresses corresponding thereto, anidentification tag corresponding to the selected sensor.

In a second embodiment of the present invention, there is provided asecond method of identifying a selected imaging sensor, where the sensorcomprises a first array of image pixels and a second array of referencepixels. The first array is configured to capture images and the secondarray is configured to permit black or dark level compensation of imagescaptured by the first array. Each reference pixel has a dark currentvalue and an address associated therewith. The second method comprisesproviding the selected imaging sensor; downloading dark signal valuesand addresses corresponding thereto from the second array; selecting,from among the dark signal values and addresses corresponding thereto,selected dark signal values and addresses corresponding thereto;generating, from the selected dark signal data and addressescorresponding thereto, an identification tag corresponding to theselected sensor, and associating the identification tag with apreviously generated identification tag stored in a computer readablemedium.

In a third embodiment of the present invention, there is a provided asystem for generating an identification tag corresponding to a selectedintegrated circuit, where the integrated circuit comprises a first arrayof image pixels and a second array of reference pixels. The first arrayis configured to capture images and the second array is configured topermit black or dark level compensation. Each reference pixel has a darkcurrent value and an address associated therewith. The system comprisesmeans for providing the selected integrated circuit; means fordownloading or measuring the dark signal levels and addresses associatedtherewith; means for selecting, from among the dark signal values andaddresses associated therewith, selected dark signal values and theaddresses associated therewith; and means for generating, from theselected dark signal values and addresses associated therewith, anidentification tag for the selected integrated circuit.

In a fourth embodiment of the present invention, there is provided athird method of generating an identification tag corresponding to aselected integrated circuit, where the integrated circuit comprises afirst array of cells or pixels and a second array of cells or pixels.The cells or pixels of the first array are configured to carry out afirst function, and the cells or pixels of the second array areconfigured to carry out a second function different from the firstfunction. Each cell or pixel in the second array has a signal level andaddress corresponding thereto. The third method comprises: providing theselected integrated circuit; downloading or measuring the signal levelsand corresponding addresses from the second array; selecting, from amongthe signal levels, selected signal levels having predeterminedcharacteristics; and generating, using the addresses corresponding tothe selected signal levels, an identification tag for the selectedintegrated circuit.

In a fifth embodiment of the present invention, there is provided afourth method of generating an identification tag corresponding to aselected means for imaging, where the imaging means comprises a firstarray of means for capturing light and a second array of masked meansfor capturing light. The first array is configured to capture images andthe second array is configured to permit black or dark levelcompensation of images captured by the first array. Each masked meansfor capturing light has a dark signal value and an address associatedtherewith. The fourth method comprises: providing the selected imagingmeans; downloading dark signal values and addresses correspondingthereto from the second array; selecting, from among the dark signalvalues and addresses corresponding thereto, selected dark signal valuesand addresses corresponding thereto; and generating, from the selecteddark signal data and addresses corresponding thereto, the identificationtag.

In a sixth embodiment of the present invention, there is provided afifth method of generating an identification tag corresponding to aselected integrated circuit (IC), where the IC comprises an array ofmemory cells, and each memory cell has an address associated therewith.The fifth method comprises: providing the selected IC; determining theaddresses of one or more defective memory cells in the selected IC;selecting, from among the addresses data locations corresponding to thedefective memory cells, selected defective memory cell addresses; andgenerating, from the selected defective addresses an identification tagcorresponding to the selected IC.

In the foregoing and other embodiments of the present invention,addresses may be provided in a (row, column) or other data locationformat familiar to those skilled in the semiconductor arts.

In the foregoing and other embodiments of the present invention,methods, and corresponding means of effecting same, may additionallycomprise, but are not limited to, one or more of: at least one ofstoring and saving the downloaded black or dark signal values andaddresses corresponding thereto; storing and saving the identificationtag in a computer readable medium; combining the initial identificationtag with other information to form combined information; determiningwhether the identification tag has been generated previously; retrievingother information associated with the identification tag; using theidentification tag to at least one of track the sensor duringmanufacturing, track the sensor after manufacturing, track sensorinventory, determine the date upon which the sensor was manufactured orshipped from the foundry, determine the particular manufacturing batchcorresponding to the sensor, determine the process, manufacturing ormaterial history corresponding to the sensor, identify manufacturingproblems associated with the sensor, identify material problemsassociated with the sensor, calculate or determine royalties associatedwith the sensor, determine which patents or licenses correspond to thesensor, determine whether an appropriate license has been taken by themanufacturer of the sensor, determine ownership of the sensor, record ordetermine the uses or applications of the sensor, improve qualitycontrol, sort the sensor, and acquire or use sensor defect or failuredata; and associating other information with the identification tag.

In the foregoing and other embodiments of the present invention,identification tags may additionally be employed to at least one oftrack an IC during manufacturing, track an IC after manufacturing, tracksensor inventory, determine the date upon which an IC was manufacturedor shipped from the foundry, determine the particular manufacturingbatch corresponding an IC, determine the process, manufacturing ormaterial history corresponding to an IC, identify manufacturing problemsassociated with an IC, identify material problems associated with an IC,calculate or determine royalties associated with an IC, determine whichpatents or licenses correspond to an IC, determine whether anappropriate license has been taken by the manufacturer of an IC,determine ownership of an IC, record or determine the uses orapplications of an IC, improve quality control, sort an IC, and acquireor use IV defect or failure data. “Other information” may be associatedwith an identification tag and may include one or more of: manufacturinginformation, date of manufacture, time of manufacture, manufacturing runnumber, type or model number of selected sensor, manufacturing plantidentification, materials or components employed, suppliers of materialsor components, shipping date, manufacturing ambient environment data,wafer or wafer batch from which selected sensor was manufactured,customer for which integrated selected sensor was manufactured,information regarding problems or particularities occurring on the dateof manufacture or during the manufacturing run, intellectual propertyroyalty, licensing or identification information, trade secretinformation, copyright information, and intellectual propertyidentification information.

BRIEF DESCRIPTION OF THE DRAWINGS

Numerous aspects of the various embodiments of the present inventionwill is become apparent from the following specification, drawings andclaims in which:

FIG. 1 shows a block diagram of one embodiment of integrated circuit 10suitable for use in the present invention;

FIG. 2 shows one embodiment of sensor 10 suitable for use in the presentinvention;

FIG. 3 shows one embodiment of imaging array 32, separation array 33 andidentification or reference array 34 suitable for use in the presentinvention;

FIG. 4 shows one embodiment of identification or reference array 34suitable for use in the present invention;

FIG. 5 shows a flow diagram according to one embodiment of a method ofthe present invention; and

FIG. 6 shows a flow diagram according to another embodiment of a methodof the present invention.

The drawings are not necessarily to scale. Like numbers refer to likeparts or steps throughout the drawings.

DETAILED DESCRIPTIONS

Set forth hereinbelow are detailed descriptions of some preferredembodiments of the present invention.

FIG. 1 shows a block diagram of one embodiment of integrated circuit 10suitable for use in the present invention. In FIG. 1, integrated circuit10 is a CMOS (complementary metal oxide semiconductor) imaging sensorcomprising row decoder 20, photosensor imaging array 30, columnamplifier 40, A/D converter 50 and image processor 60. In one embodimentof integrated circuit 10, row decoder 20 is a line address register, andcolumn amplifier 40 comprises column CDS circuits and a horizontal shiftregister that transfer analog voltages provided by photosensor imagingarray 30 to A/D converter 50. As shown in FIG. 1, integrated circuit 10includes not only photosensor imaging array 30, but further preferablyincludes a number of processing and control circuits capable ofexecuting or carrying out functions such as timing logic, exposurecontrol, A/D conversion, shutter control, white balance gain adjustmentand image processing.

Referring now to FIGS. 1 and 3, photosensor imaging array 30 typicallycomprises active pixel imaging array 32, which is employed to capturedigital images, and optically shielded pixel or identification array 34,which in the embodiment of the present invention now being described isemployed for black or dark level compensation of images captured byactive pixel area 32 (see FIG. 3). Photosensor imaging array preferablycomprises photodiode or photogate photosensitive pixel elements, andmost preferably comprises active pixel sensors having one or morephotodiodes and a readout amplifier incorporated into each pixel,thereby permitting charge accumulated in each photodiode to be convertedinto an amplified voltage inside each pixel prior to being transferredin sequential rows and columns to A/D converter 50 via column amplifier40.

For example, photosensors in arrays 33 and 34 may be covered with one ormore layers of metal oxide and/or other suitable optically opaquematerials that are preferably amenable to semiconductor manufacturingprocesses. These layers prevent the ingress of light into the individualphotosensor wells from which optically shielded array 34 and separationarray 33 are composed, thereby theoretically preventing the generationof charge and voltage that would otherwise arise from the presence oflight.

In one preferred embodiment of the present invention, active pixel array32 and identification pixel array 34 are identical with the exceptionthat array 34 has been masked, shielded or covered with metallic orother layers during the sensor die manufacturing process such thatexternal light incident upon sensor 10 cannot reach the reference pixelscontained in array 34. This permits identification or optically-shieldedarray 34 to be used for black or dark level compensation, typicallycarried out by a black or dark level compensation algorithm or framerate clamp that subtracts the average signal level of the referencepixels in array 34 from the signal levels measured in active pixel array32, thereby compensating for temperature and time-dependent dark currentnoise occurring in the active imaging pixels. Another function of array34 is to provide the addresses of high dark current pixels so as topermit an identification signature or tag unique or reasonably unique tosensor 10 to be generated, more about which we say below.

As shown in FIG. 3, optically shielded pixel array 34 is preferablyseparated from active pixel array 32 by separation pixel array 33, whichfunctions to prevent appreciable quantities of light from leakingbetween active array 32 and optically shielded array 34. Photosensors inseparation array 33 are typically optically shielded in the same manneras those in optically shielded array 34.

In active pixel imaging array 32 and identification or opticallyshielded pixel array 34, in the absence of light ideally no charge isgenerated by the photodiode or photogate corresponding to each pixel. Inpractice, however, and even in the complete absence of light, anadditional contribution to current flowing through the load transistorof each pixel is present. This additional contribution is known as thedark current and arises primarily from the leakage currents associatedwith each pixel. Dark current noise can exhibit a significant degree offluctuation from pixel to pixel, and depends heavily on ambientoperating conditions. Dark current noise increases with ambienttemperature.

Variations in dark current noise between pixels occur in opticallyshielded array 34. Such variations are partially random in nature andoccur for several reasons, including the presence of minuteimperfections in the sensor die, which in turn result from imperfectionsin manufacturing and materials. Factors that can potentially contributeto dark signal noise variation in second reference pixel array 30include, but are not limited to, variations in semiconductorcrystalline, well, layer and transistor structures, lattice defects,oxide breakdown, MOS channel surface inversion, electromigration, metalcorrosion, metal stress-voiding, soft errors due to alpha particles fromcosmic and other sources of radiation, and the presence of impurities,particulates, hot electron and high energy carriers, undesired metalsand undesired organic chemicals.

Dark current noise can be lowered using various techniques, such as theuse of pinned photodiodes in which a shallow p+layer on top of thephotodiode fills the interface states by means of holes, preventing themfrom generating dark current noise. Further information concerning darkcurrent noise may be found in: (1) “Empirical dark current modeling forcomplementary metal oxide semiconductor active pixel sensors” byShcherback et al. in Opt. Eng. 41(6) 1216-1219, June 2002; (2)“Photoresponse Analysis and Pixel Shape Optimization for CMOS ActivePixel Sensors” by Shcherback et al. in IEEE Transaction on ElectronDevices, Vol. 50, No. 11, January, 2003; and (3) “Dark Current ReductionTechniques for Wide Dynamic Range Logarithmic CMOS Pixels” by Choubey etal., accepted to the 30th International Congress of Imaging Science, pp.1-5, May 2006.

Owing to technical, cost and manufacturing reasons, it is generallypreferred that the photosensors forming the pixels of arrays 32, 33 and34 be of identical type and construction (e.g., APS photodiodes havingthe same functional characteristics and construction). Note thatphotosensor imaging array 30 is formed of rows and columns ofphotosensors such that each photosensor in array 30 has a unique address(x,y) defined by the particular row and column corresponding thereto.

Referring again to FIG. 1, photosensor imaging array 30 preferablycomprises a conventional Bayer or CMY polymeric filter array whichcovers active pixel array 32, as is well known in the art. In theconventional Bayer filter array two green pixels are provided for eachblue pixel and each red pixel. Other types of filter arrays known in theart may also be used, such as a Bayer pattern using subtractiveprimaries, a red/green/blue plus emerald filter as employed by SONY inthe DCS F828 product, a cyan, magenta, yellow and green array used insome video cameras to provide a compromise between maximum lightsensitivity and high color quality, or a yellow/cyan/green/unfilteredarray such as that employed by HITACHI and JVC in some video cameras.

When an image is acquired (or an “integration period” has beeninitiated) by sensor 10, in one embodiment of the present invention allthe pixels in active array 32 are reset, typically (but not necessarily)one row at a time, by row decoder 20, which preferably compriseson-board timing and control circuitry and line address registerfunctionality. In one embodiment, once the integration or image captureperiod has ended, the voltage generated in each pixel of arrays 32 and34 is transferred serially under control of row decoder 20 to columnamplifier 40, which typically includes a correlated double sampling(CDS) circuit to correct each pixel for reset and amplifier noise, ahorizontal shift register and an amplifier circuit.

Once gain and offset values have been assigned in the amplifier, pixelinformation is preferably shifted serially to A/D converter 50 where thepixel data are rendered into a linear digital array of binary digits.Image processor 60 receives pixel information from A/D converter 50 andperforms image recovery and processing functions thereon. For example,image processor applies a black or dark level compensation algorithm (or“frame rate clamp”) to the image pixel data, typically by subtractingthe average signal level of the optically shielded pixels, therebycompensating for temperature and time-dependant dark current noise inthe imaging pixels.

Other types of image processing may be performed on the image pixel databy image processor 60 or other components of sensor 10, including, butnot limited to, anti-aliasing filtering, white balance compensation,smoothing, sharpening, color balance, aperture control, and other signalprocessing functions. Note that image processing and other functionalitymay be incorporated into virtually any of blocks 20, 30, 40, 50 and 60shown in FIG. 1, depending on the specific circuitry and architectureactually employed in sensor 10. (See, for example, the block diagram ofone embodiment of sensor 10 shown in FIG. 2, where various types offunctionality are incorporated into many different portions of sensor10.) After the image pixel data have been sufficiently processed theymay be sent to a digital signal processor for buffering to an outputport (not shown in FIG. 1) and subsequently provided as digital output70.

Referring now to FIG. 2, there is shown one example of sensor 10 thatmay be employed according to one embodiment of the present invention.FIG. 2 shows a block diagram of an AVAGO TECHNOLOGIES ADCC-3000Landscape 1.3 megapixel ¼″ CMOS image sensor 10 with integrated imageprocessor 60. Digital output data 70 are transmitted using a parallelport. Internal FIFO data handling with automatic lowest power managementis supported to reduce output clock frequency, host processor bandwidthrequirements, power and EMI. Active pixel array 32 comprises 1,280columns and 1,024 rows of active pixels in a ¼″ format. Sensor 10 ofFIG. 2 employs 2.8 micron pixel design and is manufactured using a 0.18micron process. Not shown in FIG. 2 are optically shielded pixel array34 and separation pixel array 33, both of which are incorporated intophotosensor imaging array 30. On-chip A/D converter 50 provides up to10-bit resolution per pixel. Further details concerning the particularsensor illustrated in FIG. 2 may be found in the AVAGO TECHNOLOGIES datasheet for the ADCC-3000 product, the entirety of which is herebyincorporated by reference herein in its entirety. Another example of aproduct that may be employed in the present invention is the AVAGOTECHNOLOGIES ADCC-3850 CMOS image sensor, the AVAGO TECHNOLOGIES datasheet for which is also hereby incorporated by reference herein in itsentirety.

Referring now to FIG. 4, there is shown a schematic representation ofone embodiment of optically shielded pixel array 34 comprising an arrayof 8 rows by 1,280 columns to form a total of 10,240 optically shieldedpixels. Note that for illustrative purposes identification or opticallyshielded array 34 in FIG. 4 is not drawn to scale, and that for purposesof clarity separation array 33 and active pixel array 32 are not shownin FIG. 4. In respect of sensor 10, the vast bulk of the pixels formingarray 34 will provide dark signal values at digital output 70 that areless than 1 or 2 on a 10-bit scale. In all cases observed heretofore bythe inventors of the present invention, however, a small number ofoptically shielded pixels in array 34 will provide “bad” or high darksignal values. In the illustrative example provided in FIG. 4, darkenedpixels a through e are those pixels having the five highest dark signalvalues from among all the pixels in array 34.

It has been discovered that the spatial distribution of high dark signalvalue pixels in array 34 is approximately random due to largely randomdefects being introduced into wafers during the silicon wafermanufacturing process, as discussed above. Moreover, high dark signalvalues in shielded array 34 are characterized in having approximatelyrandom magnitudes. In accordance with one embodiment of the presentinvention, the random nature of either or both the spatial distributionsand magnitudes of high dark signal value pixels may be employed tocreate a unique or reasonably unique signature or identification tagthat is used to identify a particular sensor, integrated circuit and/ordie or chip 10.

In one embodiment of the present invention, a pre-selected number ofhighest dark signal values and their corresponding (row, column)addresses are identified from among a set of dark signal valuescorresponding to all or a portion of array 34, and a unique orreasonably unique signature or identification tag is generated on thebasis of the (row, column) addresses of the pre-selected number ofhighest dark signal value pixels.

By way of example, and continuing to refer to FIG. 4, let us assume thatthe number of pre-selected highest dark signal values is five, that thefive darkened pixels in FIG. 4 correspond to the five highest darksignal values measured from array 34, that such five highest dark signalvalue pixels have the (row, column) addresses and dark signal valuesshown in Table 1 below:

TABLE 1 Example High Dark Signal Addresses and Values Corresponding toFIG. 4 Address Measured High Dark Pixel (row, column) Signal Value a (0,1234) 60 b (1, 378) 12 c (2, 569) 14 d (3, 1125) 101 e (4, 6) 10

Note that in the case of sensor 10 being an imaging sensor, the measuredhigh dark signal value present in each pixel of array 34 will beproportional to the amount of time active pixel array 32 is exposed tolight (or “integrated”) owing to leakage currents increasing inmagnitude as exposure time increases. Note further that in the presentinvention any number of pre-selected high dark signal values may bechosen to generate an identification signature or tag, and that suchpre-selected number is not confined to the number “five.” Indeed, suchpre-selected number of high dark signal values may range between onevalue and several thousand values. Some examples of pre-selected numbersof values of the present invention may be selected from the groupconsisting of one value, two values, three values, four values, fivevalues, six values, seven values, eight values, nine values, ten values,eleven values, values between one and twenty, values between one andfifty, and values between one and two hundred.

The higher the number of pre-selected values from an identificationsignature or tag is generated, the greater the probability that theresulting identification signature or tag will be unique in respect of aset of such signatures or tags generated from a number ofmass-manufactured dies or sensors of a particular type or model.Conversely, the lower the number of pre-selected values from anidentification signature or tag is generated, the lesser the probabilitythat the resulting identification signature or tag will be unique.

It will now become apparent that the selection of the pre-selectednumber of highest dark signal values to be employed will depend on anumber of factors, including, but not limited to, the total number ofchips, sensors, dies or integrated circuits 10 of a particular model orseries that are be manufactured, the number of pixels or memory cellscontained in array 34 that are available for use, and the expectedoccurrence of measurable defects such as high dark signal values inarray 34.

Continuing to refer to FIG. 4, Table 1 and the embodiment of the presentinvention described above, we now proceed to describe one illustrativemethod of generating an identification signature or tag on the basis ofthe (row, column) addresses corresponding to the five highest darksignal values of the above example. Dark signal values stored in eachpixel of array 34 are downloaded along with image data from sensor 10via digital output 70 to computer 125 using, for example, a framegrabber operating in conjunction with a CCIR or other appropriatecommunications protocol. In computer 125, image data are separated fromdark signal data, and dark signal data values are sorted and processedin computer 125 to generate an identification signature or tag using acomputer program such as the C++ program set forth below in Table 2:

TABLE 2 C++ Program for Processing High Dark Signal Data Values andGenerating an Identification Signature or Tag functionrun_getIdTag(outfile,opt1,opt2,device,ftype) % usage %run_getIdTag(outfile,ftype); % % opt = % opt(1) = directory containingsite level % opt(2) = output choice; 0=> quiet, 1=> print tag, % outfile= output file name % ftype = input file type % % Check for number ofinputs if nargin < 1 outfile = ‘out’; opt1 = 0; opt2 = 0; device =‘pulsar_EP’; ftype = ‘bmp’; elseif nargin == 1 opt1 = 0; opt2 = 0;device = ‘pulsar_EP’; ftype = ‘bmp’; elseif nargin == 2 opt2 = 0; device= ‘pulsar_EP’; ftype = ‘bmp’; elseif nargin == 3 device = ‘pulsar_EP’;ftype = ‘bmp’; elseif nargin == 4  ftype = ‘bmp’; end if length(device)< 9 device(length(device)+1:9) = ‘’; end % %%%%%%%%%%%%%%%%%% % zdefines the image area of interest (row/column data to be processed) %z(1,1:2) => (left,right)demosic pixel row % z(1,3:4) =>(left,right)demosic pixel column % z(2,1:4) => (left,right)border pixel% z(3,1:4) => (left,right)reference and others pixel % z(4,1:4) => notused% % z2 defines where the reference pixels are % z2(1,1) > 0 => # ofrows used at start; < 0 => all % z2(1,2) > 0 => # of rows used at theend; < 0 => all % z2(2,1) > 0 => # of column used at the start; <0 =>all % z2(2,2) > 0 => # of column used at the end; <0 => all % % ifdevice(1:4) == ‘vega’ z = [0,0,0,0; 0,0,0,0; 0,0,0,0; .1,.1,.8,0.002];z2 = [4,4; −1 −1]; nn = 5; elseif device(1:5) == ‘janus’ z = [0,0,0,0;0,0,0,0; 0,0,0,0; .1,.1,.8,0.002]; z2 = [0 6; −1 −1]; nn = 5; elseifdevice(1:9) == ‘pulsar_EP’ z = [0,0,0,0; 0,0,0,0; 0,0,0,0;.1,.1,.8,0.002]; z2 = [2 10; −1 −1]; nn = 5; elseif device(1:6) ==‘pulsar’ z = [0,0,0,0; 0,0,0,0; 0,0,0,0; .1,.1,.8,0.002]; z2 = [2 10; −1−1]; nn = 5; elseif device(1:4) == ‘nemo’ z = [0,0,0,0; 0,0,0,0;0,0,0,8; .1,.1,.8,0.002]; z2 = [−1 −1; 8 8]; nn = 5; end if(ischar(opt1)) opt1 = str2num(opt1); end if (ischar(opt2)) opt2 =str2num(opt2); end opt = [opt1, opt2]; path_is = pwd; sLoc =strfind(path_is,‘\’); if opt(1) > 0 lotId =path_is(sLoc(end−2)+1:sLoc(end−1)−1); waferId =path_is(sLoc(end−1)+1:sLoc(end)−1); site = path_is(sLoc(end)+1:end);else lotId = path_is(sLoc(end−1)+1:sLoc(end)−1); waferId =path_is(sLoc(end)+1:end); site = ‘site1’; end if outfile(1:3) == ‘out’O_file = [lotId ‘w’ waferId site ‘dieId.txt’]; else O_file = [outfile‘dieId.txt’]; end z1 = sum(z(1:3,:)); fid = fopen(O_file,‘w’);fprintf(fid,‘die ID tag by pixel characteristic \n\n’); fprintf(fid,‘Lot_id|Wafer_id|Die_id|site|Id tag0|Id tag1\n’); files = dir([‘*.’ftype]); [r,c]=size(files); for i=1:r fname = files(i).name; iflength(fname) > 32 str = [‘Analysising file ..... ’, fname]; disp(str);sLoc = strfind(fname,‘_’); dieId = fname(1:sLoc(1)−1); dieId =strrep(dieId,‘_’,‘,’); if ftype == ‘bmp’ img = double(imread(fname));elseif ftype == ‘ppm’ img = double(getPpmImg(fname)); end [rr,cc,ff] =size(img); if (ff > 1) img = img(:,:,1); end if z2(1,1) < 0 imgID =img(:,:); if z2(2,1) >= 0 imgID =[imgID(:,1:z2(2,1)),imgID(:,end−z2(2,2)+1:end)]; end else imgID =[img(1:z2(1,1),:);img(end−z2(1,2)+1:end,:)]; if z2(2,1) >= 0 imgID =[imgID(:,1:z2(2,1)),imgID(:,end−z2(2,2)+1:end)]; end end [tag0,tag1] =get_idTag(imgID,nn); str2 = [lotId ‘|’ waferId ‘|’ dieId ‘|’num2str(site) ‘|’ tag0 ‘|’ tag1]; if opt(2) > 0 disp(str2); endfprintf(fid,str2); fprintf(fid,‘\n’); end end fclose(fid);

Continuing to refer to the computer program of Table 2, the programidentifies the five highest dark signal values and their corresponding(row, column) addresses and separates them from the remainder of thedark signal data. The addresses corresponding to those five highest darksignal values are then processed to yield a 20 hexadecimal stringidentification signature or tag that is unique to the sensor from whichthe dark signal data have been downloaded. The identification signatureor tag generation process begins by generating a 4-hexadecimal characterfor each of the five identified addresses: 12 least-significant bits areprovided for each specified column address (up to 4096 columnsavailable), and 4 most-significant bits are provided for each specifiedrow address (up to 16 rows). Thus, for example, pixel address “a” of(0,1234) set forth in Table 1 above is converted from (0,1234) to0h,4d2h, which in turn is cascaded into 04d2h. Similarly, addresses bthrough e in Table 1 above are converted as follows:

-   -   b: (1,378) converts to 115ch    -   c: (2,569) converts to 2239h    -   d: (3,1125) converts to 3465h    -   e: (4,6) converts to 4006h

In this example, the ID signature or tag is generated by combining thefive addresses “a” through “e” in serial ordered fashion to yield the 20hexadecimal string identification signature, which in the presentexample is:

-   -   042d115c223934654006

In respect of a high dark signal value associated with a single pixel ata fixed (row, column) address, the inventors have discovered that somevariation over time may occur in the high dark signal value. Theobserved time variation is thought to be due to naturally occurringfluctuations in the voltages presented by “bad” pixels or cells, as wellas inherent limitations in the means employed to measure such voltages.One consequence of this time variation is that the order in which highdark signal values and their corresponding addresses are arranged forprocessing to generate the identification signature or tag for a givensensor or die 10 may change depending on when, how and under whatambient conditions such data are downloaded from sensor 10. This in turnmay result in multiple but different identification signatures or tagsbeing generated for the same selected sensor 10. To preclude or minimizethis possibility, high dark signal values and addresses may bedownloaded two or more times sequentially from identification array 34of a selected sensor, integrated circuit, chip or die 10, and theresulting data sets averaged or otherwise statistically treated to yielda more repeatable and stable identification signature or tag for sensor10.

It will be understood by those skilled in the art that numerousvariations, modifications, permutations and combinations of theforegoing identification signature or tag generation scheme may beemployed with the benefit of the hindsight provided by the presentdisclosure, and that many of such variations, modifications,permutations and combinations will fall within the scope of the presentinvention.

For example, instead of converting the above five addresses tohexadecimal format they could be simply be serially combined to form the15-digit identification signature 137825693112546. Alternatively, theaddresses may be combined in a different order, or a mathematicalalgorithm may be employed to process the signatures to yield a differentalphabetic, binary, numerical, hexadecimal or other identificationsignature or tag. Only row or only column data, or only respectiveportions thereof, may be used to generate the identification signatureor tag. High dark signal values themselves (such as those listed inTable 1 above)—as opposed to high dark signal value addresses—may beemployed to generate an identification signature or tag for eachintegrated circuit 10. Or high dark signal values may be combined withcorresponding high dark signal addresses to yield an identificationsignature or tag for integrated circuit or sensor 10. More or fewer than10 bits of high dark signal data may be employed to generate anidentification signature or tag, or portion thereof, for integratedcircuit or sensor 10.

Note that high dark signal values may be processed, and identificationsignatures or tags calculated or partially calculated on-board in sensor10 by adding appropriate functionality to sensor 10.

Analog memory chips, sensors and integrated circuits, including, but notlimited to, analog EEPROM chips, volatile and non-volatile analog memorychips, integrated circuits containing flash memory cells capable ofstoring more-than-simple binary, variable information or voltages,integrated circuits with analog multi-level storage capabilities, andthe like, may likewise be adapted for use in accordance with the presentinvention. It will therefore be understood that optically shielded array34 is but one embodiment or subset of a larger set of identificationarrays 34 falling within the scope of the present invention.

The feasibility or desirability of employing some of the variousembodiments of the present invention in a given type of sensor,integrated circuit, die or chip will in many cases depend on the totalnumber of pixels, analog memory cells or memory cells that may bededicated to providing a separate array 34, as well as the statisticaloccurrence of measurable defects in the pixels or cells of such array34. These two factors will often determine whether a given sensor,integrated circuit, die or chip 10 may be identified with sufficientparticularity or uniqueness according to the pre-determined requirementsof a given die identification program. In some embodiments of thepresent invention, the possibility of the same identification signatureor tag being generated for different sensors 10 is deemed acceptablebecause of the low statistical probability of such occurring in respectof more than a handful of sensors. Under such a scenario, the risk ofmultiple identical identification signatures or tags being generated fordifferent sensors may be deemed acceptable. Accordingly, a lower numberof pixels or memory cells may be employed as a basis for generating theidentification signature or tag.

It will now become apparent that a virtually limitless number ofdifferent circuit architectures and computational techniques may beemployed to generate a unique or close-to-unique identificationsignature or tag for different types of chips, integrated circuits, diesand sensors 10 in accordance with the teachings of the presentinvention.

Referring now to FIG. 5, there is shown method 100 according to oneembodiment of the present invention. In step 110, selected integratedcircuit, sensor, chip or die 10 is provided having identification array34 incorporated therein. At step 120 selected sensor 10 is operativelyconnected to one or more devices 115 well known in the art such as asuitable frame grabber capable of downloading data residing in and/orassociated with the pixels or memory cells of identification array 34,and transferring and/or storing same to or in computer 125 in step 130.Note that once the identification data have been received from sensor 10and/or identification tag 145 has been generated, either or both may bestored in a database or other computer readable medium such as, by wayof non-limiting example, a computer hard drive, a server, floppy disk,cache memory, a pipeline, volatile or non-volatile computer memory, abuffer, RAM, SRAM or DRAM memory, EEPROM, or on a CD or DVD.

Once stored or resident in computer 125, the identification data areprocessed at step 140 to generate initial identification tag 145corresponding to selected sensor 10. In one embodiment of the presentinvention, data downloaded from identification array 34 of selectedsensor 10 are processed to yield a pre-selected number of data valueshaving pre-determined characteristics, such as those having the highestvalues, the lowest values, median values, average values, or thosefalling fall within a pre-determined range of values. In one suchembodiment of the present invention, and as discussed above, (row,column) addresses corresponding to a pre-selected number of data valueshaving pre-determined characteristics are used to calculate anidentification signature or tag corresponding to the selected integratedcircuit, sensor, chip or die 10.

Many different paths may be taken to generate identification tag 145 forselected sensor 10. For example, high dark signal values may beemployed, in combination with—or not in combination with—(row, column)address data to generate initial identification tag 145. As described inthe detailed discussion set forth above, numerous other possibilitiesexist for generating initial identification tag 145 in accordance withthe present invention, only some of which may realistically be listed ordiscussed explicitly herein owing to the vast number of possibilitiesthat will become apparent to one of ordinary skill in the art uponhaving read and understood the present disclosure.

Continuing to refer to FIG. 5, initial identification tag 145corresponding to selected sensor 10 may be saved in a computer databaseor other computer readable medium at step 150. Alternatively or inaddition to step 150, initial identification tag 145 is combined withother information 155, which comprises other pertinent or desiredinformation 155 associated with identification tag 145 and may include,but not be limited to:

-   -   Manufacturing information    -   Date of manufacture    -   Time of manufacture    -   Manufacturing run number    -   Type or model number of integrated circuit or sensor    -   Manufacturing plant identification    -   Materials or components employed    -   Suppliers of materials or components    -   Shipping date    -   Manufacturing ambient environment data (e.g., temperature, time,        etc.)    -   Wafer or wafer batch from which integrated circuit was        manufactured    -   Customer for which integrated circuit or sensor was manufactured    -   Information regarding problems or particularities occurring on        the date of Manufacture or during the manufacturing run    -   Intellectual property royalty, licensing or identification        information    -   Trade secret information    -   Copyright information    -   Intellectual property identification information    -   Other desired or relevant information pertaining to the selected        sensor, integrated circuit, die or chip

Once identification tag 145 and other information 155 corresponding toselected sensor 10 have been combined, either or both types ofinformation may be saved or stored in a computer readable medium at step170 for later retrieval. Sensor 10 may thereafter be identified at anytime and other information 155 associated therewith may be retrievedfrom computer 125.

FIG. 6 shows method 200 according to one embodiment of the presentinvention, where sensor 10 is provided at step 210, and subsequentidentification data 235 from identification array 34 are downloaded atstep 220. (Note that, with the exception of naturally occurringfluctuations in high dark signal values discussed above, subsequentidentification data 235 should be identical to initial identificationdata 125.) Subsequent identification tag 245 is generated at step 240using the same process as that originally employed to generate initialidentification tag 145 (which was previously stored in a computerreadable medium by computer 135 according to method 100 of FIG. 5).Subsequent identification tag 245 is compared to entries in the computerreadable medium via computer 135 and associated or matched with initialidentification tag 145. Other information 155 associated with initialidentification tag 145 may now be retrieved from the computer readablemedium and associated with selected sensor 10 and subsequentidentification tag 245. In such a manner, selected sensor 10 may beidentified with particularity (or at least with a reasonable degree ofparticularity), and other information 155 may be employed to effect anynumber of applications, including but not limited to:

-   -   Tracking dies during or after manufacturing    -   Tracking die inventories    -   Determining the date upon which a particular die or group of        dies was manufactured or shipped from the foundry    -   Determining the particular manufacturing batch corresponding to        a particular die    -   Determining the process, manufacturing or material history        corresponding to a sensor or integrated circuit    -   Identifying or associating manufacturing problems in particular        dies or batches of dies    -   Identifying problems in or associate materials used to        manufacture particular dies or batches of dies    -   Calculating or determining royalties    -   Determining which patents and/or licenses correspond to which        dies    -   Determining whether appropriate licenses have been taken from        the licensor by the manufacturer of a die or group of dies    -   Determining ownership of a die or group of dies    -   Recording or determining uses or applications of a die or group        of dies    -   Improving quality control during the die manufacturing process    -   Sorting dies during or after the die manufacturing process    -   Acquiring and using die defect or failure data    -   Other applications

Many different combinations, variations, adaptations and permutationsmay be made respecting the methods illustrated in FIGS. 5 and 6 and yetnevertheless fall within the scope of the present invention. Forexample, and by way of non-limiting example, computer 125 may be apersonal computer, a mainframe computer, a series of computers connectedby a network, multiple separate or connected computers, or one or moremicroprocessors, CPUs, or more processors, DSPs or controllers. Some ofthe steps illustrated in FIGS. 5 and 6 may be left out, while othersteps not shown in FIGS. 5 and 6 may be added. Other information 155need not be stored or retrieved together, stored or retrieved at thesame time, or stored or received in the same computer 125 or the samecomputer readable medium. Instead, identification tags 145 and 245should be capable of being associated with one another, as well as withother information 155 according to any of a number of methods andtechniques well known in the art.

In another embodiment of the present invention, addresses such as datalocations of “bad” or defective memory cells in flash, RAM, SRAM, DRAM,EEPROM and other types of memory chips are employed to identify suchchips in accordance with the teachings of the present invention. In suchan embodiment, an integrated circuit (“IC”) is provided comprising anarray of memory cells, where each memory cell has a unique address ordata location associated therewith. The addresses of one or moredefective memory cells in the selected IC are determined, and from amongthe addresses corresponding to the defective memory cells, selecteddefective cell addresses are selected. Next, using the selecteddefective addresses an identification tag corresponding to the selectedIC is generated, which may then be stored, saved, manipulated orotherwise used in accordance with the teachings set forth herein.

The preceding specific embodiments are illustrative of the practice ofthe invention. It is to be understood, therefore, that other expedientsknown to those skilled in the art or disclosed herein may be employedwithout departing from the invention or the scope of the appendedclaims. For example, the present invention is not limited to imagingsensors but may be employed, for example, in analog memory integratedcircuits. The present invention is not limited to CMOS sensors, and maybe employed in other types of semiconductor devices. Imaging, analogmemory or memory portions of integrated circuits may be physicallyseparated from circuitry having other types of functionality andtherefore not reside on the same integrated circuit having suchcircuitry. The present invention may also be employed in imaging sensorsusing charge coupled devices (CCDs) instead of photodiodes.

Having read and understood the present disclosure, those skilled in theart will now understand that many combinations, adaptations, variationsand permutations of known memory chips, imaging sensors and analogmemory integrated circuits may be employed successfully in the presentinvention.

In the claims, means plus function clauses are intended to cover thestructures described herein as performing the recited function and theirequivalents. Means plus function clauses in the claims are not intendedto be limited to structural equivalents only, but are also intended toinclude structures which function equivalently in the environment of theclaimed combination.

Note that in the present specification and claims, in many cases theterm “integrated circuit” (or “IC”) is intended to mean any one of an“IC,” a “sensor,” a “die” and/or a “chip.” It is to be understood thatvarious components of the ICs of the present invention and/or thedevices or computers employed to carry out the methods of the presentinvention described herein may be partitioned or distributed amongdifferent ICs, devices or computers or networks. The term “address”includes within its scope the term “data location,” as well as non-(row,column)-based addresses.

All printed publications and patents referenced hereinabove are herebyincorporated by referenced herein, each in its respective entirety.

1. A method of generating a unique identification tag corresponding to aselected imaging sensor, the sensor comprising a first array of imagepixels and a second array of reference pixels, the first array beingconfigured to capture images; the second array being configured topermit dark level compensation of images captured by the first array,each reference pixel having a dark current value and an addressassociated therewith, the method comprising: providing the selectedimaging sensor, downloading a first number of dark signal values andaddresses corresponding thereto from the second array; selecting, fromamong the first number of dark signal values and addresses correspondingthereto, a second number of selected highest dark signal values andaddresses corresponding thereto, the second number being less than thefirst number; and generating, from the second number of selected highestdark signal values and addresses corresponding thereto, a uniqueidentification tag corresponding to the selected sensor.
 2. The methodof claim 1, wherein the addresses are (row, column) addresses.
 3. Themethod of claim 1, further comprising at least one of storing and savingthe downloaded dark signal values and addresses corresponding thereto.4. The method of claim 1, further comprising at least one of storing andsaving the unique identification tag in a computer readable medium. 5.The method of claim 1, further comprising combining the initial uniqueidentification tag with other information to form combined information.6. The method of claim 1, further comprising determining whether theunique identification tag has been generated previously.
 7. The methodof claim 1, further comprising retrieving other information associatedwith the unique identification tag.
 8. The method of claim 1, furthercomprising using the unique identification tag to at least one of trackthe sensor during manufacturing, track the sensor after manufacturing,track sensor inventory, determine the date upon which the sensor wasmanufactured or shipped from the foundry, determine the particularmanufacturing batch corresponding to the sensor, determine the process,manufacturing or material history corresponding to the sensor, identifymanufacturing problems associated with the sensor, identify materialproblems associated with the sensor, calculate or determine royaltiesassociated with the sensor, determine which patents or licensescorrespond to the sensor, determine whether an appropriate license hasbeen taken by the manufacturer of the sensor, determine ownership of thesensor, record or determine the uses or applications of the sensor,improve quality control, sort the sensor, and acquire or use sensordefect or failure data.
 9. The method of claim 1, further comprisingassociating other information with the unique identification tag. 10.The method of claim 9, wherein the other information is selected fromthe group consisting of manufacturing information, date of manufacture,time of manufacture manufacturing run number, type or model number ofselected sensor, manufacturing plant identification, materials orcomponents employed, suppliers of materials or components, shippingdate, manufacturing ambient environment data, wafer or wafer batch fromwhich selected sensor was manufactured, customer for which integratedselected sensor was manufactured, information regarding problems orparticularities occurring on the date of manufacture or during themanufacturing run, intellectual property royalty, licensing oridentification information, trade-secret information, copyrightinformation, and intellectual property identification information.
 11. Amethod of uniquely identifying a selected imaging sensor, the sensorcomprising a first array of image pixels and a second array of referencepixels, the first array being configured to capture images, the secondarray being configured to permit dark level compensation of imagescaptured by the first array, each reference pixel having a dark currentvalue and an address associated therewith, the method comprising:providing the selected imaging sensor; downloading a first number ofdark signal values and addresses corresponding thereto from the secondarray; selecting, from among the firm number of dark signal values andaddresses corresponding thereto, a second number of selected highestdark signal values and addresses corresponding thereto, the secondnumber being less than the first number; generating, from the secondnumber of selected highest dark signal values and addressescorresponding thereto, a unique identification tag corresponding to theselected sensor, and associating the unique identification tag with apreviously generated identification tag stored in a computer readablemedium.
 12. The method of claim 11, wherein the addresses are (row,column) addresses.
 13. The method of claim 11, further comprising atlast one of storing and saving the downloaded dark signal values andaddresses corresponding thereto.
 14. The method of claim 11, furthercomprising at least one of storing and saving the unique identificationtag in a computer readable medium.
 15. The method of claim 11, furthercomprising combining the unique identification tag with otherinformation to form combined information.
 16. The method of claim 11,further comprising retrieving other information associated with theunique identification tag.
 17. The method of claim 11, furthercomprising using the unique identification tag to at least one of trackthe sensor during manufacturing, track the sensor after manufacturing,track sensor inventory, determine the date upon which the sensor wasmanufactured or shipped from the foundry, determine the particularmanufacturing batch corresponding to the sensor, determine the process,manufacturing or material history corresponding to the sensor, identifymanufacturing problems associated with the sensor, identify materialproblems associated with the sensor, calculate or determine royaltiesassociated with the sensor, determine which patents of licensescorrespond to the sensor, determine whether an appropriate license hasbeen taken by the manufacturer of the sensor, determine ownership of thesensor, record or determine the uses or applications of the sensor,improve quality control, sort the sensor, and acquire or use sensordefect or failure data.
 18. The method of claim 11, further comprisingassociating other information with the unique identification tag. 19.The method of claim 18, wherein the other information is selected fromthe group consisting of manufacturing information, date of manufacture,time of manufacture manufacturing run number, type or model number ofselected sensor, manufacturing plant identification, materials orcomponents employed, suppliers of materials or components, shippingdate, manufacturing ambient environment data wafer or wafer batch fromwhich selected sensor was manufactured, customer for which integratedselected sensor was manufactured, information regarding problems orparticularities occurring on the date of manufacture or during themanufacturing run, intellectual property royalty, licensing oridentification information, trade secret information, copyrightinformation, and intellectual property identification information.
 20. Asystem for generating a unique identification tag corresponding to aselected integrated circuit, the integrated circuit comprising a firstarray of image pixels and a second array of reference pixels, the firstarray being configured to capture images, the second array beingconfigured to permit dark level compensation, each reference pixelhaving a dark current value and an address associated therewith, thesystem comprising: means for providing the selected integrated circuit;means for downloading or measuring a first number of signal levels andaddresses associated therewith; means for selecting, from among thefirst number of dark signal values and addresses associated therewith, asecond number of selected highest dark signal values and the addressesassociated therewith, the second number being less than the firstnumber; and means for generating, from the second number of selectedhighest dark signal values and addresses associated therewith, a uniqueidentification tag for the selected integrated circuit.
 21. The systemof claim 20, further comprising means for at least one of storing andsaving the dark signal levels and addresses associated therewith in acomputer readable medium.
 22. A method of generating a uniqueidentification tag corresponding to a selected integrated circuit, theintegrated circuit comprising a first array of cells or pixels and asecond array of cells or pixels, the cells or pixels of the first arraybeing configured to carry out a first function, the cells or pixels ofthe second array being configured to carry out a second functiondifferent from the first function, each cell or pixel in the secondarray having a signal level and address corresponding thereto, themethod comprising: providing the selected integrated circuit;downloading or measuring a first number of signal levels andcorresponding addresses from the second array; selecting, from among thefirst number of signal levels, a second number of selected signal levelshaving predetermined characteristics indicative of pixel anomalies,defeats, or failure, the second number being less than the first number;and generating, using the addresses corresponding to the selected signallevels, a unique identification tag for the selected integrated circuit.23. The method of claim 22, wherein the predetermined characteristicsinclude highest dark signal levels.
 24. A method of generating a uniqueidentification tag corresponding to a selected means for imaging, theimaging means comprising a first array of means for capturing light anda second array of masked means for capturing light, the first arraybeing configured to capture images, the second array being configured topermit dark level compensation of images captured by the first array,each masked means for capturing light having a dark signal value and anaddress associated therewith, the method comprising: providing theselected imaging means; downloading a first number of dark signal valuesand addresses corresponding thereto from the second array; selecting,from among the first number of dark signal values and addressescorresponding thereto, a second number of selected highest dark signalvalues and addresses corresponding thereto; and generating, from thesecond number of selected highest dark signal data and addressescorresponding thereto, the unique identification tag.
 25. The method ofclaim 24, wherein the addresses are (row, column) addresses.
 26. Themethod of claim 24, further comprising at least one of storing andsaving the identification tag in a computer readable medium.
 27. Themethod of claim 24, further comprising combining the identification tagwith other information to form combined information.
 28. The method ofclaim 24, further comprising determining whether the uniqueidentification tag has been generated previously.
 29. The method ofclaim 24, further comprising retrieving other information associatedwith the unique identification tag.
 30. The method of claim 24, furthercomprising using the unique identification tag tout least one of trackthe imaging means during manufacturing, track the imaging means aftermanufacturing, track imaging means inventory, determine the date uponwhich the imaging means was manufactured or shipped from the foundry,determine the particular manufacturing batch corresponding to theimaging means, determine the process, manufacturing or material historycorresponding to the imaging means, identify manufacturing problemsassociated with the imaging means, identify material problems associatedwith the imaging means, calculate or determine royalties associated withthe imaging means, determine which patents or licenses correspond to theimaging means, determine whether an appropriate license has been takenby the manufacturer of the imaging means, determine ownership of theimaging means, record or determine the uses or applications of theimaging means, improve quality control, sort the imaging means, andacquire or use imaging means defect or failure data.
 31. The method ofclaim 24, further comprising associating other information with theunique identification tag.
 32. The method of claim 31, wherein the otherinformation is selected from the group consisting of manufacturinginformation, date of manufacture, time of manufacture manufacturing runnumber, type or model number of selected imaging means, manufacturingplant identification, materials or components employed, suppliers ofmaterials or components, shipping date, manufacturing ambientenvironment data, wafer or wafer batch from which selected imaging meanswas manufactured, customer for which integrated selected imaging meanswas manufactured, information regarding problems or particularitiesoccurring on the date of manufacture or during the manufacturing run,intellectual property royalty, licensing or identification information,trade secret information, copyright information, and intellectualproperty identification information.